FIG. 30 is a block configuration diagram of a contactless power transmission system of the related art described in PTL 1.
As illustrated in FIG. 30, in PTL 1, contactless power receiver 401 is disclosed in which input of a command and output of information with respect to contactless power feeder 420 are performed in order to improve usability and reliability of contactless power receiver 401.
Contactless power receiver 401 includes resonant circuit for power reception 405a which becomes a power reception unit for receiving power fed from contactless power feeder 420 over the wireless on the basis of a change in a magnetic flux generated at the time of operating contactless power feeder 420, and resonant circuit 405b performing bidirectional communication of a communication signal with respect to contactless power feeder 420 over the wireless.
Contactless power feeder 420 includes resonant circuit for feeding power 422 corresponding to resonant circuit 405a, and resonant circuit for communication 421 and communication circuit 423 corresponding to resonant circuit 405b. 
FIG. 31 is a block configuration diagram of a wireless charge system of the related art described in NPL 1 in which, in particular, the specification for a mobile device such as a smart phone is defined.
As illustrated in FIG. 31, the wireless charge system defined in NPL 1 includes base station 301 and mobile device 302.
Power is fed from power conversion unit 306a and power conversion unit 306b of base station 301 to power pickup unit 307 of mobile device 302 over the contactless. Load 309 of mobile device 302 consumes the fed power.
At this time, base station 301 adjusts the amount of fed power according to the amount of required power which is transmitted from power receiver 305 of mobile device 302 to power transmitter 304a and power transmitter 304b of base station 301 through communication control unit 308a and communication control unit 308b. 
FIG. 32 is a state transition diagram of the wireless charge system of the related art described in NPL 1. In selection state S1 illustrated in FIG. 32, it is detected whether or not mobile device 302 is disposed on base station 301.
The detection of mobile device 302, for example, is performed by detecting a change in impedance, or the like. In a case where base station 301 detects that mobile device 302 is disposed thereon, the state is transitioned to ping state S2. In ping state S2, a minute amount of power which is sufficient to activate communication control unit 308c is fed to power pickup unit 307 of mobile device 302 from power conversion unit 306a. 
In this state, in a case where a response from mobile device 302 is not returned to base station 301 through communication control units 308a and 308b, the state returns to selection state S1.
In a case where the response returns, base station 301 is transitioned to identification state/setting state S3 while continuously transmitting a minute amount of power.
In identification state/setting state S3, mobile device 302 transmits identification information or the amount of required power to base station 301 through communication control units 308a and 308b. In a case where it is determined that it is possible to correspond to the amount of required power from mobile device 302, base station 301 is transitioned to power feeding state S4.
In power feeding state S4, power transmission is performed from power transmitter 304a of base station 301 to power receiver of mobile device 302. The amount of power to be transmitted is adjusted according to the amount of required power which is transmitted from power receiver 305 of mobile device 302 to power transmitter 304a of base station 301. Load 309 of mobile device 302 consumes the transmitted power.
FIG. 33 illustrates a format of a communication packet which is used in the wireless charge system described in NPL 1.
As illustrated in FIG. 33, preamble 321 stores codes of 11 bits to 25 bits for detecting the communication packet. Header 322 stores a code of 1 bite corresponding to a class and a size of a message.
Message 323 stores data items of 1 bite to 27 bites corresponding to the codes in header 322. Checksum 324 stores data of 1 bite for detecting a communication error.
FIG. 34 is a diagram illustrating a relationship between a message size and a code of a header defined in NPL 1. FIG. 35 is a diagram illustrating a message type defined in NPL 1.
In NPL 1, it is defined that message sizes of 1 bite to 27 bites which are obtained by substituting the code in header 322 into a numerical expression illustrated in FIG. 34 are used. In addition, as illustrated in FIG. 35, in NPL 1, a packet type of a message and a message size corresponding to each code are defined. Here, the detailed description thereof is omitted.